Method for cleaning gas turbines



Jan. 22, 1963 'u. c. WALK ETAL 3,074,822

METHOD FOR CLEANING GAS TURBINES Filed April 22, 21.960

38 2o 7 Es |o H INVENTORS FRANKLIN E. WAL/fl? (CLIFFORD WALK A T TORNEY Unite This invention relates in general to a method for cleaning surfaces by abrasive and other cleaning action. More specifically the invention relates to a method for remotely cleaning and removing industrial grirnes and combustion products from surfaces, particularly from the blades and other parts of gas turbines in jet propulsion engines.

The invention provides a method for cleaning the interiors of gas turbines, without dismantling the same, by techniques which in some respects resembles sand blasting but which attain entirely different consequences. In order to accomplish this a material is provided, frozen dioxane or similar chemical or combinations of crushed frozen dioxane and Dry Ice, which has hitherto unknown desirable characteristics such as efiective abrasive action by physical contact in the solid form plus solvent action of the abraded deposits and yet sublimes or vaporizes quickly after application, leaving no residue. A blasting method and apparatus are provided to maintain and direct the how of the sublimating abrasive composition without melting.

The industrial cleaning of machinery and equipment is a large one as attested by the number of commercial solvents and cleaners available. In particular the aircraft industry has large and specialized needs in this field. Aside from passenger service and comfort, upon which revenues depend, the success of operations largely depends upon the maintenance of flying equipment in near perfect working order. This latter is of course of great importance in military aircraft. In order to insure long hours of trouble-free flight, engines must be kept in excellent mechanical condition. This includes minimization of engine deposits brought about mainly from incomplete combustion of fuels. More specifically this is of great importance in jet engines as deposits occur on the turbine blades and their proper cleaning and removal is of the utmost importance. Irregularities in fuel mixtures and burning conditions result :in solid carbonaceous materials being deposited onto the blades and other areas. Deposits from the lead products added to the fuel are particularly offensive. A certain amount of lubricating oil is also consumed in these areas which adds to the deposits by coking and incomplete burning actions. Industrial grimes and other impurities in the air contribute a lesser extent to surface deposits on turbine rotors and also on compressors, fans, fuel injectors and other parts in jet propulsion engines.

The deleterious effect upon the jet engine of such deposits is apparent. Because of the high exhaust and air speeds, undesirable irregularities in fluid flow are brought about. Uneven deposits on blades and rotors cause an unbalanced condition which may increase Wear on bearings and other parts. Perhaps more important, the irregular air floW over the blades can result in compressor blade stall which can cause flame-out. Tolerances are altered between close working parts, and the general performance and working condition of the engine is altered and decreased rapidly approaching unsafe and dangerous operation.

Such deposits must be periodically removed. This is part of a routine maintenance procedure in which the entire jet propulsion engine is removed from the aircraft frame and transported to a shop where it is first disassembled. Each part is thereafter treated to clean and rates Patent add restore the part to its original condition, inspected and acceptable parts are used to rebuild the engine. Tr'eat ment for individual parts often includes special dips or sprays with corrosive paint remover, application of heated caustic or acid, and even erosive sand blasting when all other methods fail. Even on a large scale the procedure is expensive, time-consuming and wasteful of individual parts. Since engine deposits are frequently the immediate factor needing correction, engines are often taken out of service prior to the time when a general overhaul would be scheduled. It is therefore apparent that any method of cleaning and removing such deposits Without engine removal and dismantling would result in large economies in time and money and reduce reserve engine needs as well. The need is particularly obvious when the information is added that there are many airbases flying tens of thousands of jet engines. Correction of these several problems would serve commercial as well as military needs, since the fast growing potential of commercial aircraft using jet engines is rapidly replacing the internal combustion engines.

The need for a method for remotely cleaning engines is particularly pointed out in Item No. 556, Cleaning Process to Remove Deposits from Turbine Blades Without Disassembly of Engine, in a bulletin entitled Technical Items Affecting the National Defense, published by the National Inventors Council, Washington, D.C., and available from the US. Department of Commerce, Washington, DC. Quoting the bulletin, it is stated:

A material is desired which can be applied while the engine is turning over and which by chemical or other action loosens carbon, dirt and lead deposits from the blades. Ground nut shells and Fullers earth are usable except for contamination of oil. A harmless chemical is therefore indicated.

Various materials have been tried in an effort to dislodge the deposited material without scouring or pitting engine surfaces, followed by flushing therefrom, e.g., rice hulls, moth ball crystals, ice and Dry Ice. Each material was successful in some degree, as would be expected of any abrasive material, but each had harmful disadvantages. For example the rice hulls created a harmful action in contact with lubricating oils; the moth balls were highly toxic; and the ice and Dry Ice did not have a proper capacity for good abrasive and solvent action. None of these materials were satisfactory, and as indicated by the gomernment bulletin mentioned above, neither the materials nor the methods provided sufiicient cleaning action to avoid periodic disassembly at less frequent intervals than would otherwise be necessary.

It is amongst the objects of the present invention to provide a method for cleaning remote surfaces, such as the interior of engines where direct access cannot be obtained and the residue from abrasive materials cannot be satisfactorily removed.

It is a further object of this invention to provide a method which will permit standardization of cleaning application for all jet aircraft engines.

It is also an object of this invention to provide a method for removing industrial grime, films and deposits from surfaces by combined blasting and solvent techniques without consequent injury to such surfaces.

It is a further object of the present invention to :pro vide a method for removing deposits from remote parts of jet engines without disassembly of the engine.

It is a further object of this invention to provide a method for mixing and fluidizing frozen dioxane and Dry Ice and projecting the same upon surfaces requiring clean- It is a further object of this invention to use a composi- 3 tion of matter for cleaning remote surfaces which will increase the smoothness of the surfaces being cleaned.

Still another object of the invention is to provide a method for remotely cleaning jet engine interiors by introducing fluidized mixtures of crushed frozen dioxane and Dry Ice into the engine while being operated by an auxiliary power unit.

It is also an object of the invention to provide a method for mixing and fluidizing frozen dioxane and Dry Ice and projecting same into jet engine interiors or against other surfaces to be cleaned.

Further objects are to provide a construction of maximum simplicity, economy, and ease of manufacture, also such further objects, advantages and capabilities as will fully appear and as are inherently possessed by the device and the invention described herein.

Invention further resides in the combination, construction and arrangement of parts illustrated in the accompanying drawings, and While there is shown therein a preferred embodiment thereof, it is to be understood that the same is merely illustrative of the invention and that the invention is capable of modification and change, and comprehends other details of construction without depanting from the spirit thereof or the scope of the appended claims.

Referring to the drawings:

FIGURE 1 is a vertical section of the apparatus in schematic form, taken on the line I-I of FIGURE 2.

FIGURE 2 is a rear elevational view of the apparatus shown in FIGURE 1.

Referring now more particularly to the drawings, in which like reference numerals indicate like parts in the several views, the housing of the apparatus is generally indicated as 10. This housing 16 in turn is mounted on a platform 11, which is supported by two side wheels 1'12 placed forward of the platform center, which are mounted on wheel supports 16 with a single axle 17. Attached at the bottom and to the rear of the platform 11 are two rests 13, the outer ends of which raise upward and outward from the rear of the platform 11 so as to function as handles, in the manner of a wheelbarrow. At the terminus of each handle are hand grips 14.

The housing is composed of four principal sections, the motor section 28, the storage-feed section in, the conveyor section 32., and the slinger section 34.

The storage feed section 18 is shown as being rectangular, the inside of which is constructed in the form of a four-sided pyramidal hopper 19. The upper opening of the hopper 19 is provided with a tightly fitting cover 21 having a handle 22 for easy removal. At the bottom or delivery end 23 of the hopper, there is an outlet gate 24, which is mounted in any suitable manner such as a spring-held pivot 26, so that the gate may be opened to any degree and closed at the will of the operator. A corresponding recess 27 is provided for receiving the gate 24 when it is either partially or entirely opened. The exterior sides 24 of the hopper 19, the under side of the cover 21, and around the conveyor section 32, are in sulated with some suitable material such as fiberglass, the insulation being designated 19a.

The conveyor section 32 is located directly beneath the feed chamber 19 and is in direct communication therewith by means of the hopper opening 23, but controlled, of course, by the movable outlet gate 24. Within the conveyor section 32 is a horizontal screw conveyor mounted on a shaft 31 which is coupled to and rotated by the motor 30. The shaft 3-1 is journaled for rotation at 32a in the conveyor section and at the other end at 3111 in the slinger section.

The motor 30 is firmly secured by bolts 11a or other suitable means to the platform 11 within the motor section 28, shown with a hood and positioned to the rear of the gravity feed chamber 18, the louvers 29 being side ventilators for the motor section.

Forward of the feed section 18 and axially aligned wit-h respect to the conveyor section 321 is the slinger section 34-, shown as a relatively flat cylindrical chamber having a tangential outlet 37. Within the slinger housing 34 is a bladed slinger fan 36 which is mounted on and rotated by the shaft 31. A flexible tube or hose 38 of suitable length is attached to the outlet 37. A full throated nozzle 3-9 is attached at the delivery end of the hose 33 and a hand shut-off lever 39a is provided adjacent thereto if desired. A hose hook or rack 38a is provided at a convenient place along the forward wall of the housing 18, so that the hose may be readily available, but properly cared for when not in use.

Attached adjacent one of the handles 14 is a switch box 46) having a motor switch 41 and a lever 42 for operating the hopper gate 24 for opening the same any desired degree and closing. Suit-able cords and wires 43 pass along the member 13 to the motor 3% and the hopper gate 24 for the proper control thereof. Since the controls are standard equipment and can be varied to meet any required condition, they are only indicated schematically.

The method of cleaning contemplated by this invention and for which this equipment was specifically originated, is one employing both mild abrasive and chemical solvent action in which a particular composition of matter in solid form is propelled against the contaminated surfaces, preferably while they are in motion if possible, with the consequent loosening and removal of the contaminating deposits. At the same time, through the chemical solvent action the removed material is reduced to a relatively harmless vapor and carried off in the flow of gas. When cleaning a jet engine for example, the propelling force is preferably supplemented by the rotation of the engine. The jet engine while still in its operating installation and environment is rotated by auxiliary power without introduction of fuel into the burner and without any problems resulting from heat. The cleaning composition utilized is propelled into the compressor where the solid particles abrade by contact, while others change their state to a liquid and coat the surfaces contacted to engage in solvent action. The material in different phases, solid, liquid and vapor passes through the combustion chamber into the turbine and out the exhaust nozzle in the form of an easily dispersible vapor-gas mixture. It will be observed that deposits from any and all of these areas which are removed by the abrasive action and by the solvent action, are carried by the material in a vapor-gas phase to the discharge, leaving no residue whatsoever in the engine. Any possible residue of the material not moved by the flow created in the delivery force and the rotation of the engine, vaporizes in a very short time, leaving the engine surfaces clean and operable for extended periods of time without further maintenance.

It makes little difference whether the engine is of the jet turbine, turbojet or turbofan type. In each instance the major portion of the contaminating deposits will be on the turbine, particularly to the rear of the combustion unit. Accordingly, the major contact and work of the material is in this zone. To a lesser extent contamination resulting from combustion products, grimes and other materials, is found in the compressors, fans, and other parts. The ramjet, of course, does not ordinarily contain a turbine unit in the main combustion zone, but nevertheless has extensive contaminated areas which need frequent cleaning. Accordingly, the same is included.

The main contaminating deposits result from incomplete combustion of petroleum products as well as the lead substances added to the fuel, decomposition products thereof, and the cooking and burning of the lubricating oils and products thereof. The contaminating deposits are principally formed by the intense heat of the engine, which may be as high as 1400 F., or more, in the central flame, and 600 F. on some metal surfaces.

The preferred chemical cleaning material used for this operation is dioxane. This chemical is known also as 1,4-dioxane, diethylene ether, 1,4-diethylene dioxide, diethylene oxide and dioxyethylene ether. It is an inflammable, colorless, stable liquid, miscible with water and most organic solvents, having a boiling point of l.3 C. and a freezing point of 11.8 C. Liquid commercial dioxane is readily available from numerous sources. The dioxane used for the present invention is in the solid phase and to get it to the required solid form, the material is frozen and crushed. While the cleansing agent may be frozen and crushed dioxane, it is preferable to mix it with crushed Dry Ice to maintain the crystalline structure of the dioxane for an extended period of time and effectively prevent excessive vaporization or other changes of state prior to contact with rearward and remote areas to be cleaned.

Frozen dioxane and Dry Ice are preferably mixed in a ratio of 50% each by volume, although this ratio may be varied to meet special conditions. The mixture is crushed or otherwise comrninuted to an average particle size not to exceed /2 inch. An average particle size of approximately inch appears to produce optimum results in most instances.

Since dioxane is an inflammable material, the fire hazard in both storage and handling is a real and substantial obstacle. The addition of the Dry Ice in formulating the cleaning material has many unexpected useful advantages and consequences. The low temperature of the Dry Ice maintains the crystalline structure of the dioxane enabling the material to do effective work in all of its phases during the entire travel through the engine. Dry Ice also enhances and shortens the time factor in the change of state of the dioxane from liquid to vapor which greatly enhances its solvent action of converting the contaminating deposits to liquid and then to vapor state for discharge. Since Dry Ice sublimates to the vapor state directly at about 200 times the volume of the solid state, it provides an enormous gas volume for carrying off the contaminates both in solid and vapor form. The propulsion of the Dry Ice particles against the contaminated surfaces also assists in abrasive action. Of great importance also is the fire extinguishing effect of the liberated carbon dioxide gas which acts as a built-in fire extinguished for the dioxane, making the mixture completely safe for handling and use in the cleaning as well as providing the necessary safety factor against the danger of fire when the engine is later started and tested before being released for use after cleaning. This is especially important when it is remembered that the cleaning and testing are accomplished without the necessity of removing the engine from its useful environment, such as an aircraft.

The operation of the invention is as follows. When a jet engine, for example, is ready for cleaning, there is no need to remove the same from the aircraft. Because of the very short time required to clean the contaminated areas of the engine by the present invention, there is practically no lost time for the aircraft.

The hopper 19 of the apparatus shown in FIGURES l and 2 is charged with solid Dry Ice and dioxane, crushed to the appropriate size desired and in the ratio desired as set forth above. The material can either be mixed in the storage or holding facility or introduced separately into the hopper in the proportions desired. The insulation of the hopper l9 permits the moving of the equipment to the required location while preserving the solid state of the cleaning material. The gate 24, of course, is in the closed position, closing the outlet 23 for the hopper. The vehicle is then moved to the location of the engine to be cleaned and preferably adjacent the engines air intake. The motor 30 is connected to a suitable electrical source of energy and started, so as to drive the screw conveyor means 33 and the fan 36 in the slinger housing 34. The flexible hose 38 and the nozzle 39 are then positioned and held so as to be aimed directly into the engine through the air intake. Because of the low temperatures involved with Dry Ice, it is advisable to handle the hose and the nozzle with suitable gloves to prevent frost bite. It is also apparent that the nozzle 39' may be held in any required position by suitable clamps (not shown) which may be attached to the air intake rim, for example. As indicated earlier, it is advisable to rotate the jet engine and it will be assumed for purposes of this description that this is done by auxiliary power so that heat problems will not be involved. When everything is in readiness, the gate 24 is opened to the extent the operator deems necessary, from the hand control 42 on the handle. This allows the material in the hopper 19 to feed into the screw conveyor 13, thence into the rotating fan 36 and out through the flexible hose 38 to be forcefully discharged by the nozzle 39. A control 39a is provided at the nozzle merely as a safety means to stop the flow of material therethrough and provide time to turn off the motor and feed mechanism at the hand controls.

It will be observed that the force generated by the delivery of the solid material fro mthe nozzle 35 will be directed to the moving engine and propelled with such force as to contact the surfaces of all of the interior of the engine. The contact includes both particles of dioxane and Dry Ice. The dioxane and Dry Ice by physical contact generated by the propulsion force and enhanced by the rotation of the engine, is sufficient to loosen some of the contamination and in this contact some of the dioxane changes to the liquid state to coat the surfaces. Also, some of the Dry Ice sublimates to form an enormous volume of gas which bears solid particles of both Dry Ice and dioxane through the remainder of the engine and parts, while at the same time carrying off loose contaminants freed by the contact. The liquid phase of the dioxane coating the parts acts as a solvent to further clean the contaminated portions and this, in turn, is either carried off in very small droplets or rapidly vaporized by the large volume of carbon dioxide gas through the engine and out through the exhaust outlet of the engine. It will be observed that every portion of the engine is subject to the action of this material, whether it be abrasive or solvent in character and that the areas of greatest action are usually those of greatest contamination.

A standard jet engine is completely cleaned in a period of about one minute of application in this manner. Furthermore, not only are the harmful deposits removed from the surface of the engine parts but there is a completely unexpected benefit in that the smoothness of the turbine blades and other parts is increased. This is a result which is highly desirable even when deposits are not present. The very definite superior physical results from this method of cleaning are further emphasized by the economic advantages. Jet engines may be cleaned by the present method in a very few minutes including the time required to get the equipment to location and in operation, at a cost of less than $50.00, as compared with more than $1,000.00 in the normal period of ten days for disassembly, cleaning and assembly.

Although the description has been directed largely to jet engines, it is obvious that it is not restricted solely to the cleaning of such engines, but is generally useful for any abrasive and solvent cleaning of industrial grimes, films and carbonation deposits, especially in remote or hard to get at locations. It may also be used in place of sand blasting where the special characteristics of this invention, i.e., mild abrasion and solvent action, are particularly useful.

We claim:

1. A method for cleaning and removing contaminating deposits on the metal surfaces of jet engines having a forward air intake and a rear exhaust outlet and the like comprising the steps of propelling a cleaning material containing frozen dioxane in comminuted form at the air intake and exhausting the gas-vapor containing the removed deposits at the exhaust outlet.

2. A method for cleaning and removing contaminating deposits on the metal surfaces of jet engines having a forward air intake and a rear exhaust outlet and the like comprising the steps of rotating the engine by auxiliary power, propelling a cleaning material containing frozen dioxane and Dry Ice having a particle size averaging about one-half inch in diameter at the air intake and exhausting the gas-vapor containing the removed deposits at the exhaust outlet.

3. A method for cleaning and removing contaminating deposits on the metal surfaces of jet engines having a forward air inlet and a rear exhaust outlet and the like by both mild abrasive and chemical solvent action comprising the steps of rotating the engine by auxiliary power, propelling a cleaning material containing frozen dioxane and Dry Ice in equal parts by volume having a particle size averaging about one-half inch in diameter at the air intake and exhausting the gas-vapor containing the removed deposits at the exhaust outlet.

4. A method for cleaning and removing contaminating deposits on the metal surfaces of jet engines having a forward air intake and a rear exhaust outlet and the like by both mild abrasive and chemical solvent action without removing the engine from its operating environment, comprising the steps of rotating the engine by auxiliary power, propelling a cleaning material containing frozen dioxane and Dry ice in equal parts by volume having a particle size averaging about one-ha1f inch in diameter at the air intake and exhausting the gas-vapor containing the removed deposits at the exhaust outlet.

5. The method of cleaning and removing contaminating deposits from the metal surfaces of turbines and the like without removal from their operating environment or disassembly, comprising the steps of propelling a mixture of crushed frozen dioxane and crushed Dry Ice in equal parts by volume into the inlet of a turbine and rotating said turbine by auxiliary power, whereby said mixture in its various states is forced through said turbine, contacting and removing deposits from the metal surfaces thereof by both mild abrasive action and chemical solvent action.

References Cited in the file of this patent UNITED STATES PATENTS 1,529,379 Thompson Mar. 10, 1925 2,342,991 Wiltoff Feb. 29, 1944 2,378,815 WikOff June 19, 1945 2,601,608 Hansen -2 June 24, 1952 2,698,265 Klingel Dec. 28, 1954 2,699,403 Courts Jan. 11, 1955 2,701,220 Smith Feb. 1, 1955 

1. A METHOD FOR CLEANING AND REMOVING CONTAMINATING DEPOSITS ON THE METAL SURFACES OF JET ENGINES HAVING A FORWARD AIR INTAKE AND A RARE EXHAUST OUTLET AND THE LIKE COMPRISING THE STEPS OF PROPELLING A CLEANING MATERIAL CONSISTING FROZEN DIOXANE IN COMMINUTED FORM AT THE AIR INTAKE AND EXHAUSTING THE GAS-VAPOR CONTAINING THE REMOVED DEPOSITS AT THE EXHAUST OUTLET. 